Method and system for split voltage domain transmitter circuits

ABSTRACT

Methods and systems for a photonically enabled complementary metal-oxide semiconductor (CMOS) chip are disclosed and may comprise in an integrated circuit comprising a driver: amplifying a received signal in a plurality of partial voltage domains, and generating the partial voltage domains by controlling a voltage domain boundary value between two partial voltage domains utilizing a differential amplifier that samples an output voltage of a cascade amplifier that is an input to the driver and controls a current supplying said cascade amplifier. A series of diodes may be driven in differential mode via the amplified signals. An optical signal may be modulated via the diodes, which may be integrated in a Mach-Zehnder modulator or a ring modulator. The diodes may be connected in a distributed configuration. The amplified signals may be communicated to the diodes via transmission lines, which may be even-mode coupled.

CROSS-REFERENCE TO RELATED APPLICATIONS/INCORPORATION BY REFERENCE

This application is a continuation of application Ser. No. 14/229,243,which is a continuation of application Ser. No. 12/208,650 filed on Sep.11, 2008, now U.S. Pat. No. 8,687,981, which in turn makes reference to,claims priority to and claims the benefit of U.S. Provisional PatentApplication No. 60/997,282 filed on Oct. 2, 2007.

This application also makes reference to:

-   U.S. Pat. No. 7,039,258; and-   U.S. patent application Ser. No. 12/208,668 filed on even date    herewith.

Each of the above stated applications is hereby incorporated herein byreference in its entirety.

FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[Not Applicable]

MICROFICHE/COPYRIGHT REFERENCE

[Not Applicable]

FIELD OF THE INVENTION

Certain embodiments of the invention relate to integrated circuit powercontrol. More specifically, certain embodiments of the invention relateto a method and system for split voltage domain transmitter circuits.

BACKGROUND OF THE INVENTION

Electronic circuits typically require a bias voltage for properoperation. The voltage level required by a circuit depends on theapplication. A circuit for signal transmission may require a highervoltage than a circuit used for processing data. The optimum voltage maybe determined by the bias voltage requirements of the transistors, orother active devices, within the circuit.

A bipolar transistor circuit may require a higher voltage in amplifierapplications to avoid saturation of the amplifier, as opposed toswitching operations, for example. CMOS circuits may require a lowervoltage to drive the MOSFETs in the circuit.

Furthermore, as device sizes continue to shrink for higher speed andlower power consumption, a high voltage may degrade performance andcause excessive leakage. With thinner gate oxides, gate leakage currentmay become significant using historical bias voltages, thus driving gatevoltages lower. However, if a transmitter/receiver may be integrated inthe same device, a higher bias voltage may also be required. Biasvoltages are typically DC voltage, and may be supplied by a battery.However, there may be noise in the bias voltage, which may be mitigatedby capacitive filters. The variable output voltage of batteries myaffect operation of battery powered devices. Devices generally must becapable of operating over a large range of voltage due to the variableoutput voltage capability of batteries.

Further limitations and disadvantages of conventional and traditionalapproaches will become apparent to one of skill in the art, throughcomparison of such systems with the present invention as set forth inthe remainder of the present application with reference to the drawings.

BRIEF SUMMARY OF THE INVENTION

A system and/or method for split voltage domain transmitter circuits,substantially as shown in and/or described in connection with at leastone of the figures, as set forth more completely in the claims.

Various advantages, aspects and novel features of the present invention,as well as details of an illustrated embodiment thereof, will be morefully understood from the following description and drawings.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a block diagram of a photonically enabled CMOS chip, inaccordance with an embodiment of the invention.

FIG. 1B is a diagram illustrating an exemplary CMOS chip, in accordancewith an embodiment of the invention.

FIG. 1C is a diagram illustrating an exemplary CMOS chip coupled to anoptical fiber cable, in accordance with an embodiment of the invention.

FIG. 1D is a block diagram of an exemplary n-type field effecttransistor circuit, in accordance with an embodiment of the invention.

FIG. 1E is a block diagram of an exemplary p-type field effecttransistor circuit, in accordance with an embodiment of the invention.

FIG. 2 is a block diagram of an exemplary split domain Mach-Zehndermodulator, in accordance with an embodiment of the invention.

FIG. 3 is a schematic of an exemplary transmission line driver with adomain splitter circuit, in accordance with an embodiment of theinvention.

FIG. 4 is an exemplary stacked inverter unit driver, in accordance withan embodiment of the invention.

FIG. 5 is a block diagram of exemplary coupled transmission lines, inaccordance with an embodiment of the invention.

FIG. 6 is a flow chart illustrating exemplary steps in the operation ofa Mach-Zehnder modulator with partial voltage domains, in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Certain aspects of the invention may be found in a method and system forsplit voltage domain transmitter circuits. Exemplary aspects of theinvention may comprise amplifying a received signal in a plurality ofpartial voltage domains. Each of the partial voltage domains may beoffset by a DC voltage from the other partial voltage domains. A sum ofthe plurality of partial domains may be equal to a supply voltage of theintegrated circuit. A series of diodes may be driven in differentialmode via the amplified signals. An optical signal may be modulated viathe diodes, which may be integrated in a Mach-Zehnder modulator or aring modulator, for example. The diodes may be connected in adistributed configuration. The amplified signals may be communicated tothe diodes via even-mode coupled transmission lines. The partial voltagedomains may be generated via stacked source follower or emitter followercircuits. The voltage domain boundary value may be at one half thesupply voltage due to symmetric stacked circuits.

FIG. 1A is a block diagram of a photonically enabled CMOS chip, inaccordance with an embodiment of the invention. Referring to FIG. 1A,there is shown optoelectronic devices on a CMOS chip 130 comprising highspeed optical modulators 105A-105D, high-speed photodiodes 111A-111D,monitor photodiodes 113A-113H, and optical devices comprising taps103A-103K, optical terminations 115A-115D, and grating couplers117A-117H. There is also shown electrical devices and circuitscomprising transimpedance and limiting amplifiers (TIA/LAs) 107A-107D,analog and digital control circuits 109, and control sections 112A-112D.Optical signals are communicated between optical and optoelectronicdevices via optical waveguides fabricated in the CMOS chip 130.

The high speed optical modulators 105A-105D comprise Mach-Zehnder orring modulators, for example, and enable the modulation of the CW laserinput signal. The high speed optical modulators 105A-105D are controlledby the control sections 112A-112D, and the outputs of the modulators areoptically coupled via waveguides to the grating couplers 117E-117H. Thetaps 103D-103K comprise four-port optical couplers, for example, and areutilized to sample the optical signals generated by the high speedoptical modulators 105A-105D, with the sampled signals being measured bythe monitor photodiodes 113A-113H. The unused branches of the taps103D-103K are terminated by optical terminations 115A-115D to avoid backreflections of unwanted signals.

The grating couplers 117A-117H comprise optical gratings that enablecoupling of light into and out of the CMOS chip 130. The gratingcouplers 117A-117D are utilized to couple light received from opticalfibers into the CMOS chip 130, and the grating couplers 117E-117H areutilized to couple light from the CMOS chip 130 into optical fibers. Theoptical fibers may be epoxied, for example, to the CMOS chip, and may bealigned at an angle from normal to the surface of the CMOS chip 130 tooptimize coupling efficiency.

The high-speed photodiodes 111A-111D convert optical signals receivedfrom the grating couplers 117A-117D into electrical signals that arecommunicated to the TIA/LAs 107A-107D for processing. The analog anddigital control circuits 109 may control gain levels or other parametersin the operation of the TIA/LAs 107A-107D. The TIA/LAs 107A-107D thencommunicate electrical signals off the CMOS chip 130.

The control sections 112A-112D comprise electronic circuitry that enablemodulation of the CW laser signal received from the splitters 103A-103C.The high speed optical modulators 105A-105D require high-speedelectrical signals to modulate the refractive index in respectivebranches of a Mach-Zehnder interferometer (MZI), for example. Thevoltage swing required for driving the MZI is a significant power drainin the CMOS chip 130. Thus, if the electrical signal for driving themodulator may be split into domains with each domain traversing a lowervoltage swing, power efficiency is increased.

FIG. 1B is a diagram illustrating an exemplary CMOS chip, in accordancewith an embodiment of the invention. Referring to FIG. 1B, there isshown the CMOS chip 130 comprising electronic devices/circuits 131,optical and optoelectronic devices 133, a light source interface 135,CMOS chip surface 137, an optical fiber interface 139, and CMOS guardring 141.

The light source interface 135 and the optical fiber interface 139comprise grating couplers that enable coupling of light signals via theCMOS chip surface 137, as opposed to the edges of the chip as withconventional edge-emitting devices. Coupling light signals via the CMOSchip surface 137 enables the use of the CMOS guard ring 141 whichprotects the chip mechanically and prevents the entry of contaminantsvia the chip edge.

The electronic devices/circuits 131 comprise circuitry such as theTIA/LAs 107A-107D and the analog and digital control circuits 109described with respect to FIG. 1A, for example. The optical andoptoelectronic devices 133 comprise devices such as the taps 103A-103K,optical terminations 115A-115D, grating couplers 117A-117H, high speedoptical modulators 105A-105D, high-speed photodiodes 111A-111D, andmonitor photodiodes 113A-113H.

FIG. 1C is a diagram illustrating an exemplary CMOS chip coupled to anoptical fiber cable, in accordance with an embodiment of the invention.Referring to FIG. 1C, there is shown the CMOS chip 130 comprising theelectronic devices/circuits 131, the optical and optoelectronic devices133, the light source interface 135, the CMOS chip surface 137, and theCMOS guard ring 141. There is also shown a fiber to chip coupler 143, anoptical fiber cable 145, and a light source module 147.

The CMOS chip 130 comprising the electronic devices/circuits 131, theoptical and optoelectronic devices 133, the light source interface 135,the CMOS chip surface 137, and the CMOS guard ring 141 may be asdescribed with respect to FIG. 1B.

In an embodiment of the invention, the optical fiber cable may beaffixed, via epoxy for example, to the CMOS chip surface 137. The fiberchip coupler 143 enables the physical coupling of the optical fibercable 145 to the CMOS chip 130.

The light source module 147 may be affixed, via epoxy or solder, forexample, to the CMOS chip surface 137. In this manner a high power lightsource may be integrated with optoelectronic and electronicfunctionalities of one or more high-speed optoelectronic transceivers ona single CMOS chip.

The power requirements of optoelectronic transceivers is an importantparameter. Minimizing voltage swings is one option for reducing powerusage, and modulating light at multi-gigabit speeds typically requireshigher voltages than needed for high-speed electronics. Thus, amulti-voltage domain architecture in the modulator driver circuitryreduces the voltage requirements, and thus improved power efficiency, bydriving the circuitry in each domain over a smaller voltage range thanthe entire voltage swing.

FIG. 1D is a block diagram of an exemplary n-type field effecttransistor circuit, in accordance with an embodiment of the invention.Referring to FIG. 1D, there is shown a source follower circuit 55comprising an n-channel field effect transistor (NFET) 50, a resistor33, a high rail 20, and a low rail 10. There is also shown a circuitinput 100 and a circuit output 200.

The source follower circuit 55 has two power rails, comprising the highrail 20 biased at a voltage V_(f), or full voltage, and the low rail 10,marked with the customary symbol of “ground”. The circuit has an input100 on the gate of the NFET 50, while the circuit output 200 is on theNFET source side, or simply source. The NFET 50 drain side, or drain, isconnected to the high rail 20. The resistor 33 is coupled between thesource terminal of the NFET 50 and the low rail 10, completing anelectrical path between the high 20 and low 10 rails.

In operation, an input signal is applied to the input 100. The sourcefollower circuit 55 may be utilized to lower the impedance level in thesignal path, drive resistive loads, or to provide DC level shifting,since the gate-source DC voltage drop may be controllable by the biascurrent. The gain of the source follower circuit 55 may be near unity,resulting in a AC output signal at the circuit output 200, but with aconfigurable DC output level.

FIG. 1E is a block diagram of an exemplary p-type field effecttransistor circuit, in accordance with an embodiment of the invention.Referring to FIG. 1E, there is shown a source follower circuit 65comprising a p-channel field effect transistor (PFET) 60, a currentsource 33′, a high rail 20, and a low rail 10. There is also shown acircuit input 100′ and a circuit output 200′.

The PFET source follower has two power rails, comprising a high rail 20at a voltage V_(f), or full voltage, and a low rail 10, marked with the“ground” symbol. The circuit has an input 100′ on the PFET 60 gate,while the circuit output 200′ is on the PFET 60 source side, or simplysource. The PFET 60 drain side, or drain, is connected to the low rail10. The current source 33′ is coupled to the high rail 20 and the PFET60 source, completing an electrical path between the high 20 and low 10rails.

In operation, an input signal is applied to the input 100′. The sourcefollower circuit 65 may be utilized to lower the impedance level in thesignal path, drive resistive loads, or to provide DC level shifting,since the gate-source DC voltage drop may be controllable by the biascurrent. The gain of the source follower circuit 65 may be near unity,resulting in a similar AC output signal at the circuit output 200′, butwith a configurable DC output level.

FIG. 2 is a block diagram of an exemplary split domain Mach-Zehndermodulator, in accordance with an embodiment of the invention. Referringto FIG. 2, there is shown a split-domain Mach-Zehnder modulator (MZM)250 comprising a transmission line driver 209, waveguides 211,transmission lines 213A-213D, diode drivers 215A-215H, diodes 219A-219D,and transmission line termination resistors R_(TL1)-R_(TL4). There isalso shown voltage levels V_(dd), V_(d), and Gnd. In an embodiment ofthe invention, V_(d) is equal to a voltage of V_(dd)/2, thus generatingtwo voltage domains, due to the symmetric nature of the stackedcircuits. However, the invention is not limited to two voltage domains.Accordingly, any number of voltage domains may be utilized, dependent onthe desired voltage swing of each domain and the total voltage range,defined here as V_(dd) to ground. Similarly, the magnitude of thevoltage range in each voltage domain may be a different value than otherdomains.

The transmission line (T-line) driver 209 comprises circuitry fordriving transmission lines in an even-coupled mode, where the signal oneach pair of transmission lines is equal except with a DC offset. Inthis manner, two or more voltage domains may be utilized to drive thediodes that generate index changes in the respective branches of the MZM250. In another embodiment of the invention, the T-line driver 209 maydrive transmission lines in odd-coupled mode. Even-coupled mode mayresult in a higher impedance in the transmission line, whereasodd-coupling may result in lower impedance.

The waveguides 211 comprise the optical components of the MZM 250 andenable the routing of optical signals around the CMOS chip 130. Thewaveguides 211 comprise silicon and silicon dioxide, formed by CMOSfabrication processes, utilizing the index of refraction differencebetween Si and SiO₂ to confine an optical mode in the waveguides 211.The transmission line termination resistors R_(TL1)-R_(TL4) enableimpedance matching to the T-lines 213A-213D and thus reducedreflections.

The diode drivers 215A-215H comprise circuitry for driving the diodes219A-219D, thereby changing the index of refraction locally in thewaveguides 211. This index change in turn changes the velocity of theoptical mode in the waveguides 211, such that when the waveguides mergeagain following the driver circuitry, the optical signals interfereconstructively or destructively, thus modulating the laser input signal.By driving the diodes 219A-219D with a differential signal, where asignal is driven at each terminal of a diode, as opposed to one terminalbeing tied to AC ground, both power efficiency and bandwidth may beincreased due to the reduced voltage swing required in each domain.

In operation, a CW optical signal is coupled into the “Laser Input”, anda modulating differential electrical signal is communicated to theT-line driver 209. The T-line driver 209 generates complementaryelectrical signals to be communicated over the T-lines 213A-213D, witheach pair of signals offset by a DC level to minimize the voltage swingof each diode driver 215A-215H, while still enabling a full voltageswing across the diodes 219A-219D.

Reverse biasing the diodes 219A-219D generates field effects that changethe index of refraction and thus the speed of the optical signalpropagating through the waveguides 213A-213D. The optical signals theninterfere constructively or destructively, resulting in the “ModulatedLight” signal.

FIG. 3 is a schematic of an exemplary transmission line driver with adomain splitter circuit, in accordance with an embodiment of theinvention. Referring to FIG. 3, there is shown a transmission line(T-line) driver 300 and transmission lines 307A-D. The T-line driver 300may be substantially similar to the T-line driver 209 described withrespect to FIG. 2 and comprises a domain splitter 310, amplifiers305A/305B, current sources 303A-303E, a comparator 301, bias resistorsR_(B1) and R_(B2), resistors R_(T1) and R_(T2), a capacitor C₁, andMOSFET transistors M₁-M₅. The domain splitter 310 may be a pair ofstacked source-follower pairs comprising the MOSFET transistors M₆-M₉.

The T-line driver 300 comprises a cascode circuit that may be enabled togenerate the complementary inputs V+ and V− to be communicated to thedomain splitter 310, although a cascode circuit is not required. Theoutputs V+ and V− are inverted relative to V_(in)+ and V_(in)−, and maybe of smaller magnitude. Components of the circuit, such as NFETs,resistors, capacitors, and others may be so selected that the outputvoltages V+ and V− are approximately centered around the voltage V_(d)in FIG. 2, typically set to be half of the full range voltage:V_(d)=V_(dd)/2, due to the symmetric nature of the stacked circuits.

The cascode T-line driver 300 may employ elements for feedback to assurethe stability of the outputs, and to correct for processing variationsin the circuits. Such a feedback element may be the differentialamplifier 301 controlling the gate of MOSFET transistor M₁, which mayact like an adjustable resistance in parallel with the capacitor C₁. Inanother embodiment of the invention, the MOSFET transistor M1 may act asan adjustable current source.

The differential amplifier 301 is sensitive to the magnitude and to theimbalances of the outputs V+ and V−, sampling the voltage via the twotap resistors R_(T1) and R_(T2) and comparing the sampled voltage to areference voltage, which may be chosen to be V_(d), which is equal toV_(dd)/2 in this exemplary embodiment. However, V_(d), could be chosento be any voltage within the voltage range defined by V_(dd) and ground.

The domain splitter 310 comprises a pair of stacked NFET and PFET sourcefollower circuits. The drain side of the NFET M7 and the drain side ofthe PFET M6 are commonly connected to V_(d), or V_(dd)/2 in thisexemplary embodiment. In this manner, the NFET source followers M7 andM9 are in the lower voltage domain, powered by V_(dd)/2 to ground, whilethe PFET source followers M6 and M8 are in the higher voltage domain,powered by V_(dd) to V_(dd)/2.

The input voltages to the amplifiers 305A and 305B are coupled byelectrically connecting the gate of the NFET M7 to the gate of the PFETM6, and the gate of the NFET M9 to the gate of the PFET M8. Thisarrangement results in the tracking of output voltages, such that ifvoltage V+ rises, then both voltages V_(H) and V_(L) will rise, andconversely, if voltage V+ falls, voltages V_(H) and V_(L) will alsofall, thus exhibiting identical AC characteristics, but with a DC offsetconfigured by the domain splitter 310. The full range of voltage V+ isgenerally not restricted to either the lower or the upper voltagedomain. The rate of voltage movement, or swing, on V+, in general, isnot the same as for V_(H) and V_(L). The ratios of the swings betweenvoltages V+ and V_(H) and V_(L), respectively, depend on particulardesign and characteristics of the NFET and PFET source followers.However, this arrangement allows for voltage V_(L) to essentially coverthe span of the lower voltage domain, namely between “ground” and V_(d),and for voltage V_(H) to essentially cover the span of the upper voltagedomain, namely between V_(dd) and V_(d).

The transmission lines 307A-307D are even-coupled, in that the “+”output of both the amplifiers 305A and 305B drive coupled transmissionlines. Similarly, the “−” output of both amplifiers 305A and 305B driveanother pair of coupled transmission lines, as described further withrespect to FIG. 5.

FIG. 4 is a schematic of an exemplary stacked inverter unit drivercircuit, in accordance with an embodiment of the invention. Referring toFIG. 4, there is shown the unit driver circuit 400 comprising theinverters 401A-401Q. The unit driver circuit 400 is substantiallysimilar to one stage of diode drivers, 215A-D or 215E-215H, as describedwith respect to FIG. 2.

The input signals to the unit driver circuit 400 comprise the signalsreceived from transmission lines, such as the transmission lines307A-307D, described with respect to FIG. 3. The outputs of each pair ofstages, such as 401A-410H, and 401I-401Q, may be coupled to a diode,indicated by D1+/D1− and D2+/D2−. The voltage powering the upper stagesof the unit driver circuit 400 is defined by V_(dd) to V_(dd)/2, andV_(dd)/2 to ground for the lower stages. In this manner, each inverterstage only swings across half the entire voltage range, V_(dd)/2 in thisexemplary embodiment, while the diodes coupled to D1+/D1− and D2+/D2−are driven across the entire voltage range V_(dd) to ground.

FIG. 5 is a block diagram of exemplary coupled transmission lines, inaccordance with an embodiment of the invention. Referring to FIG. 5,there is shown ground plane 501, coupled line positive 503, coupled linenegative 505, and coupling ports 507A-507H. The transmission linescomprise a coupled line positive 503 and a coupled line negative 505transmission line and may be defined by coplanar conductive lines on theCMOS chip 130, described with respect to FIG. 1, and surrounded on bothsides by the ground plane 501. In this manner, high frequency electricalsignals may be communicated over the transmission lines of acharacteristic impedance, with each pair of complementary signals beingidentical but with a DC offset. Driving the transmission lines ineven-coupled mode may result in a higher characteristic impedance. Thecoupling ports 507A-507H enable the coupling of signals out of thetransmission lines to unit drivers, such as the unit drivers describedwith respect to FIG. 4.

FIG. 6 is a flow chart illustrating exemplary steps in the operation ofa Mach-Zehnder modulator with partial voltage domains, in accordancewith an embodiment of the invention. In step 603, after start step 601,a differential electrical signal may be applied to the T-line driver 209and a CW optical signal may be coupled to the waveguide 211 of the MZM250. In step 605, the electrical signal may be amplified by differentvoltage domain circuitry to reduce the voltage swing in each domain andthe signal may be communicated via transmission lines 213A-213D. In step607, the signal received from the transmission lines 213A-213D may beutilized to drive stacked inverter stages 215A-215H, which in turn drivethe MZM diodes 219A-219D. In step 609, the MZM diodes 219A-219D maycause constructive and/or destructive interference of the opticalsignals in the waveguides 211, such that a modulated optical signal maybe generated, followed by end step 611.

In an embodiment of the invention, a method and system are disclosed foramplifying a received signal in a plurality of partial voltage domains.Each of the partial voltage domains may be offset by a DC voltage fromthe other partial voltage domains. A sum of the plurality of partialdomains may be equal to a supply voltage of the integrated circuit 130.A series of diodes 215A-215H may be driven in differential mode via theamplified signals. An optical signal may be modulated via the diodes215A-215H, which may be integrated in a Mach-Zehnder modulator 250 or aring modulator. The diodes 215A-215H may be connected in a distributedconfiguration. The amplified signals may be communicated to the diodes215A-215H via even-mode coupled transmission lines 307A-307D. Thepartial voltage domains may be generated via stacked source followerM6-M9 or emitter follower circuits. The voltage domain boundary valuemay be at one half the supply voltage due to symmetric stacked circuits.

While the invention has been described with reference to certainembodiments, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted withoutdeparting from the scope of the present invention. In addition, manymodifications may be made to adapt a particular situation or material tothe teachings of the present invention without departing from its scope.Therefore, it is intended that the present invention not be limited tothe particular embodiments disclosed, but that the present inventionwill include all embodiments falling within the scope of the appendedclaims.

What is claimed is:
 1. A method for processing signals, the methodcomprising: in an integrated circuit comprising a driver: amplifying areceived signal in a plurality of partial voltage domains; andgenerating said partial voltage domains by controlling a voltage domainboundary value between two partial voltage domains utilizing adifferential amplifier that samples an output voltage of an amplifierthat tracks an input to the driver and controls a current supplying acascade amplifier.
 2. The method according to claim 1, comprisingdriving a series of diodes in differential mode via said amplifiedsignals.
 3. The method according to claim 2, comprising modulating anoptical signal via said diodes.
 4. The method according to claim 2,wherein said diodes are integrated in a Mach-Zehnder modulator.
 5. Themethod according to claim 2, wherein said diodes are integrated in aring modulator.
 6. The method according to claim 2, wherein said diodesare connected in a distributed configuration.
 7. The method according toclaim 2, comprising communicating said amplified signals to said diodesvia transmission lines.
 8. The method according to claim 7, wherein saidtransmission lines are even-mode coupled.
 9. The method according toclaim 1, comprising generating said partial voltage domains via stackedsource follower circuits.
 10. The method according to claim 1,comprising generating said partial voltage domains via stacked emitterfollower circuits.
 11. The method according to claim 1, comprisinggenerating said voltage domain boundary value of one half the supplyvoltage via symmetric stacked circuits.
 12. A system for processingsignals, the system comprising: one or more circuits comprising adriver, said one or more circuits being operable to: amplify a receivedsignal in a plurality of partial voltage domains; and generate saidpartial voltage domains by controlling a voltage domain boundary valuebetween two partial voltage domains utilizing a differential amplifierthat samples an output voltage of an amplifier that is an input to thedriver and controls a current supplying a cascade amplifier.
 13. Thesystem according to claim 12, wherein said one or more circuits isoperable to drive a series of diodes in differential mode via saidamplified signals.
 14. The system according to claim 13, wherein saidone or more circuits is operable to modulate an optical signal via saiddiodes.
 15. The system according to claim 13, wherein said diodes areintegrated in a Mach-Zehnder modulator.
 16. The system according toclaim 13, wherein said diodes are integrated in a ring modulator. 17.The system according to claim 13, wherein said diodes are connected in adistributed configuration.
 18. The system according to claim 13, whereinsaid one or more circuits is operable to communicate said amplifiedsignals to said diodes via transmission lines.
 19. The system accordingto claim 18, wherein said transmission lines are even-mode coupled. 20.The system according to claim 12, wherein said one or more circuits isoperable to generate said partial voltage domains via stacked sourcefollower circuits.
 21. The system according to claim 12, wherein saidone or more circuits is operable to generate said partial voltagedomains via stacked emitter follower circuits.
 22. The system accordingto claim 12, wherein said one or more circuits is operable to generatesaid voltage domain boundary value of one half the supply voltage viasymmetric stacked circuits.
 23. The system according to claim 12,wherein said one or more circuits comprises an integrated circuit.